You should aim for 6 slots for resources AS A MINIMUM (7 is better), hence a warehouse is a good first pick

You don't need both gems and elisir to win, one of the two buildings is enough

Specialists that provide additional resources on a gather action (like tanner) are a good pick at the beginning, but they get worse as the game goes on

You don't *need* the king's statue to win, 4 is a fair bet on average (also consider the master buildings available before bidding)

Try to maximize every action (for example: don't build a building if you cannot afford a specialist too; try to craft two items of the same quest when possible)

Cards: red ones are bad at the beginning; in the last turns you could go for red cards, depending on the game you have played